Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!watmath!watcgl!jdchrist
From: jdchrist@watcgl.waterloo.edu (Dan Christensen)
Newsgroups: comp.sys.sgi
Subject: questions about drawing polygons
Keywords: polygons
Message-ID: <9753@watcgl.waterloo.edu>
Date: 17 May 89 15:25:14 GMT
Distribution: comp
Organization: U of Waterloo, Ontario
Lines: 30

I have a couple of questions regarding the drawing of filled polygons
on an Iris 4D/120GTX.

1) Using the fastest settings of the lighting model (single light source
   at infinity, viewer at infinity), how many shaded polygons can be
   drawn per second?  (I know that this is a difficult question, but a
   rough figure would be useful).

2) I am trying to draw a large mesh of shaded triangles.  The GT
   Library has routines for drawing triangular meshes.  These
   routines look like they would speed up drawing significantly because
   only one third of the lighting calculations need to be done and one
   third of the data needs to be put into the pipeline, compared to
   drawing each triangle separately.  The problem I found with these
   routines is that you have no control over the order in which the
   vertices are drawn so that backface removal becomes useless.
   Turning off backface removal results in an overall slowing in the
   drawing.  Is there any way to specify the order in which the
   vertices are drawn?  It would be a shame if there isn't because
   these routines look like they could speed things up greatly.  Is
   there a way to do the same thing manually?  Could the program draw
   each vertex and save the colours calculated by the hardware and then
   draw the polygons with the lighting model turned off, using the
   precalculated colours?

Thanks for any help.

----
Dan Christensen, Computer Graphics Lab,	         jdchrist@watcgl.uwaterloo.ca
University of Waterloo, Waterloo, Ont.	         jdchrist@watcgl.waterloo.edu